输入正整数N，输出1到N之间的奇数之和

program jhgkl;
var
　　n, s, i:integer;
begin
　　read(n);
　　s := 0;
　　for i := 1 to n do
　　　　if i mod 2 = 1 then
　　　　　　s := s+i;
　　writeln(s);
end.

=================== OR ===================

program jhgkl;
var
  n, s, i : integer;
begin
  write('Please input a number: ');
  readln(n);
  if n mod 2 = 1 then n := n+1;
  s := 0;
  for i := 1 to n div 2 do
      s := s+(i+i-1);
  writeln(s);
  readln;
end.

=================== OR ===================

program jhgkl;
var
  n, s, i : integer;
begin
  write('Please input a number: ');
  readln(n);
  if n mod 2 = 1 then n := n+1;
  s := 0;
  for i := 1 to n div 2 do
      s := s+i;
  writeln(s + s - n div 2);
  readln;
end.